Prevalence of subclinical vitamin D deficiency in different European countries.

Abstract

Long-lasting and severe vitamin D deficiency leads to osteomalacia, a metabolic bone disease characterized by typical biochemical abnormalities (low serum concentrations of calcium and phosphate, increased activity of alkaline phosphatase). Bone histology shows decreased mineralization of bone matrix, increased osteoid volume and decreased bone formation. Vitamin D deficiency can be confirmed by measuring the serum concentration of 25-hydroxyvitamin D (25(OH)D), which is the major circulating metabolite bound with high affinity to a binding protein (DBP) and representing the storage form of vitamin D. In patients with osteomalacia, serum 25(OH)D levels are usually below 5 ng/ml and often undetectable. In contrast, patients with primary osteoporosis usually have serum concentrations of calcium and phosphate within the normal range, and alkaline phosphatase is rarely elevated. Therefore, in the opinion of many authors vitamin D deficiency is not an important pathogenetic factor for the development of osteoporosis. However, growing evidence demonstrates that moderately low levels of vitamin D can already have unfavorable effects on calcium homeostasis leading to bone loss, even if osteomalacia is not present. BargerLux and coworkers [1] showed that 25(OH)D contributes to the stimulation of enteral calcium absorption explaining the secondary increase in parathyroid hormone resulting from vitamin D deficiency, although 1,25-dihydroxyvitamin D (1,25-(OH)2D) levels may still be normal. A vitamin D status insufficient to maintain physiologic calcium homeostasis, but not resulting in overt osteomalacia, is called vitamin D insufficiency or subclinical vitamin D deficiency. Vitamin D insufficiency is a common problem especially in Europe (for reasons explained below), and therefore this paper will review the vitamin D status in different European countries. Definition of ‘Subclinical’ Vitamin D Deficiency